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Efficacy of intravenous prasinezumab versus placebo in Parkinson's disease patients with severe GBA mutation: a 104‑week randomized double‑blind study

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What is this trial about?

A plain-language summary of the goals, design and what participants do

A study is being carried out in people who have Parkinson’s disease that is linked to a severe change in the GBA gene. The experimental medicine being tested is called prasinezumab, which is given through an IV infusion (a drip placed into a vein). A comparable solution containing only salt water is used as a placebo. The main goal of the trial is to see whether the medicine can help protect thinking and memory abilities from getting worse over time.

Participants will receive a series of study visits over about two years. During the visits, the assigned treatment (either the medicine or the control solution) is administered by IV infusion at set intervals, and simple tests of thinking, memory and daily functioning are performed to check for any changes. Safety checks, such as blood tests and heart monitoring, are also done regularly to ensure the treatment is well tolerated. The overall design of the trial keeps both the participants and the study staff unaware of which treatment is being given, to provide an unbiased comparison.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Randomization to treatment group

    After enrollment, assignment to either the prasinezumab group or the placebo group is made without knowing which group is received.

    The assignment determines whether the infusion will contain 1500 mg of prasinezumab or 250 ml of a saline solution.

  2. Step 2

    Initial iv infusion

    The first iv infusion is performed in a clinical setting.

    If assigned to the active group, the infusion contains 1500 mg of prasinezumab in a solution for infusion.

    If assigned to the placebo group, the infusion contains 250 ml of sterile saline solution.

  3. Step 3

    Regular infusion visits

    Subsequent infusions are scheduled throughout the study period lasting 104 weeks.

    Each visit follows the same procedure as the initial infusion, using the same dose and volume assigned at randomization.

    The exact interval between infusions is defined by the study protocol and continues until week 104.

  4. Step 4

    Periodic cognitive assessments

    At designated visits, cognitive function is evaluated using standardized tests.

    These assessments measure memory, attention, executive function, visuospatial ability, and language.

    The primary result focuses on the change in cognitive score at the end of 104 weeks.

  5. Step 5

    Safety monitoring

    Regular safety laboratory tests, including blood counts and chemistry, are performed to detect any abnormal values.

    Electrocardiogram (ecg) recordings are taken to monitor heart rhythm.

    Blood pressure and heart rate are measured, including orthostatic changes, at each visit.

  6. Step 6

    Final assessment and study completion

    At week 104, a comprehensive evaluation includes the final cognitive assessment, safety laboratory tests, and ecg.

    The data collected determine the efficacy of prasinezumab compared with the placebo in preventing cognitive decline.

Who can join the trial?

6 criteria

  • Be diagnosed with Parkinson’s disease according to the official criteria set by the Movement Disorder Society (MDS).
  • Have a known heterozygous severe GBA mutation, meaning one copy of a specific gene (GBA) is changed in a way linked to Parkinson’s disease; this also includes people who have the GBA risk variant called E326K.
  • Score at least 21 on the Montreal Cognitive Assessment (MoCA), a short test that checks thinking and memory abilities.
  • Have a Hoehn and Yahr (HY) stage of 3 or lower while “ON” medication, meaning your Parkinson’s symptoms are not too severe when your medication is working.
  • Be between 35 and 80 years old when you sign the study’s written consent form.
  • Be able and willing to sign a written consent form and follow the study rules, which follow guidelines from the International Council for Harmonization (ICH) and local regulations.

Who cannot join the trial?

31 criteria

  • Known pathogenic mutation carriers of the Parkinson’s disease genes PRKN, PINK1, DJ1, or LRRK2 are not allowed.
  • Anyone who has previously received an investigational vaccine for Parkinson’s disease (including active vaccines or passive treatments using monoclonal antibodies) cannot join.
  • People who have taken part in any prior study of prasinezumab or other drugs that target the protein alpha‑synuclein are excluded.
  • Individuals with a Parkinson‑like condition other than typical Parkinson’s disease (such as progressive supranuclear palsy, multiple system atrophy, drug‑induced Parkinsonism, essential tremor, or primary dystonia) are not eligible.
  • Anyone who received any non‑Parkinson’s investigational product, device, or participated in a non‑Parkinson’s drug study within 90 days (or five drug half‑lives, whichever is longer) before the start of this trial cannot enroll.
  • Receiving any monoclonal antibody or investigational immune‑modulating drug within 180 days (or five half‑lives) before baseline—examples include monoclonal antibodies, intravenous immunoglobulin (IVIG), interleukin‑2, interleukin‑12, interferon, or other immunosuppressive medicines—excludes participation.
  • Use of immune‑modulating drugs such as oral corticosteroids within 90 days before baseline is not allowed.
  • Allergy or known severe reaction to any component of prasinezumab (such as citrate, trehalose, or polysorbate 20) or a prior infusion‑related reaction to another monoclonal antibody disqualifies a participant.
  • Any condition that makes a brain MRI unsafe or impossible (for example, severe claustrophobia not relieved by reassurance, metal implants, or certain dental work) excludes the person if an MRI has not been done within the past two years.
  • Donating more than 500 mL of blood within the three months before screening is a reason for exclusion.
  • For those who wish to give an optional spinal‑fluid sample (lumbar puncture), any of the following prevents participation: clotting problems (INR > 1.4 or platelets < 120,000/µL), infection at the puncture site, use of anticoagulant medication within 10 days, severe spine arthritis, suspected brain blockage or mass, or a history of spinal injury.
  • Pregnant or breastfeeding women, and women who could become pregnant, must have a negative pregnancy test and are excluded.
  • People under legal guardianship or supervision are not eligible.
  • Individuals who are not fluent in the national language cannot take part.
  • Residents of nursing homes or assisted‑care facilities are excluded.
  • A diagnosis of any major central nervous system disease other than Parkinson’s disease disqualifies a participant.
  • Participation in any other interventional clinical trial (studies testing a new treatment) at the same time is not allowed.
  • Past, current, or planned (within two years) treatment with deep brain stimulation (DBS) or brain ablation using focused ultrasound excludes enrollment.
  • History of a brain MRI showing a large bleed or stroke greater than 1 cm³, more than three small strokes, or severe white‑matter disease (Fazekas grade III) makes a person ineligible.
  • Any other disease, condition, or treatment that could interfere with the study or pose an unacceptable risk, including: a. Autoimmune diseases (unless very mild and well‑controlled), b. Cancer diagnosed within the past five years (except certain early‑stage skin cancers, treated cervical carcinoma in situ, non‑metastatic prostate cancer, or stage I uterine cancer), c. Active infection at screening, d. Alcohol or drug abuse within the last year (nicotine use is allowed, but marijuana in any form is not), e. Fever within one week before the first dose, f. Current major psychiatric disorders that could affect study participation (such as severe depression, schizophrenia, bipolar disorder, or mental retardation), g. Active suicidal thoughts with intent or plan.
  • Specific heart problems exclude participation, including: a. Heart attack (myocardial infarction) within the past 12 months, b. Uncontrolled slow heart rate (bradycardia) on more than one occasion in the past three months, c. Resting pulse over 110 beats per minute, d. Uncontrolled high blood pressure on more than one occasion in the past three months, e. Serious cardiovascular disease such as unstable chest pain, severe heart failure, or dangerous irregular heart rhythms.
  • Significant abnormal lab test results at screening exclude a person, including: a. Liver enzymes (ALT, AST) or bilirubin more than twice the normal limit, b. Kidney test (creatinine) more than 1.5 times the normal limit, c. Low blood counts (hematocrit, neutrophils, or platelets) or INR > 1.4, d. Abnormal thyroid‑stimulating hormone (TSH) level, e. Positive urine drug screen for illegal substances (with specific rules for prescribed medications), f. Positive test for hepatitis B, hepatitis C, or HIV (unless the infection has been successfully treated as specified).
  • If taking Parkinson’s symptom medicines, the dose of dopamine agonists, MAO‑B inhibitors, COMT inhibitors, amantadine, or levodopa must have been stable for at least 90 days before baseline (continuous levodopa pumps are acceptable if stable).
  • Women of childbearing potential who are not using a highly effective birth‑control method (failure rate < 1 % per year) during the study and for at least 90 days after the last dose cannot enroll.
  • Anyone who is unable to read or write for any reason is excluded.
  • People with Gaucher’s disease who are receiving enzyme‑replacement therapy or substrate‑reduction therapy are not eligible.
  • Use of anti‑epileptic medication for non‑seizure reasons without a stable dose for at least 90 days before baseline excludes participation.
  • Use of antidepressant or anxiolytic medication without a stable dose for at least 90 days before baseline also excludes a participant.
  • Use of any of the following drugs within 90 days before baseline disqualifies a person: typical antipsychotics, metoclopramide, flunarizine, amoxapine, amphetamine‑type drugs, reserpine, mazindol, methamphetamine, methylphenidate, norephedrine, phentermine, phenylpropanolamine, modafinil, alpha‑methyldopa, or cocaine (amantadine, quetiapine, and clozapine are allowed if stable).
  • Prior or current participation in a disease‑modifying investigational trial that involved surgery or stem‑cell therapy for Parkinson’s disease excludes enrollment.
  • Prior or current participation in any investigational trial of symptomatic or disease‑modifying Parkinson’s treatment within 90 days (or five half‑lives) before baseline is a reason for exclusion.
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Investigated drugs

prasinezumab is an experimental intravenous antibody therapy being tested in people with Parkinson's disease who have a specific genetic mutation (GBA). The medication is given through a drip into a vein and is designed to target abnormal proteins that may contribute to brain changes. In this trial, researchers are looking to see if prasinezumab can help slow or prevent the decline in thinking and memory abilities over a two‑year period.

What is already known about the treatment

  • Prasinezumab

    Prasinezumab is given as an intravenous infusion of a sterile solution, typically administered through a vein over a set period. It is still an experimental drug, currently being studied in clinical trials for Parkinson’s disease, especially in patients with a GBA gene mutation. The antibody is designed to attach to the protein alpha‑synuclein, helping the immune system clear it and potentially slowing disease progression. It belongs to the class of monoclonal antibodies used as disease‑modifying agents in neurodegenerative disorders.

  • Sodium chloride

    Sodium chloride is supplied as a sterile isotonic saline solution for intravenous infusion, poured into a vein using a standard IV set. It is an approved, widely used medication for fluid and electrolyte replacement in many medical situations. The solution simply provides water and salt to restore body fluid balance and does not act on disease pathways. It is classified as an electrolyte solution and a basic supportive therapy.

Investigated diseases

Parkinson's disease - Parkinson's disease is a chronic brain disorder that primarily affects movement. It develops gradually, starting with subtle tremor, stiffness, or slowed motions. Over time, symptoms may spread to include balance problems and difficulty with daily activities. The condition also often involves changes in thinking and memory as it advances. The disease progresses at different rates for each person, with symptoms becoming more noticeable over many years. It is caused by loss of specific nerve cells that produce a chemical important for smooth muscle control.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IITrial ID2024-513496-40-00Protocol codePreCoDe / BN45387Estimated enrolment120 patientsSponsorUniversitaetsklinikum Tuebingen AöR

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